In Fig. REF A, one flagellum was removed from each of two wildtype CR cells by careful mechanical shearing (Materials and Methods),
so that a CR-like arrangement comprising one cis and one trans flagellum is assembled.
Despite similarity with the wildtype configuration, no sustained IP breaststrokes were obtained.
Closely separated (\(<\!\!5\)  \(\mu \) m) pairs exhibit periods of phase locking.
Beat frequencies of these flagella are found to be more noisy than their counterparts in intact CR cells,
and consequently measured phase-locking is not robust (\(S=0.08\) ).
The conditional (stroboscopic) phase \(\chi \)  (Fig. REF A) is peaked weakly about \(\pi \)  indicating a tendency for AP synchronization, but the IP state is also possible.
This bistability is not species-specific;
we rendered uniflagellate [see also [1]}] pairs of pipette-held VC somatic cells (normally biflagellate)
and placed them in a similar configuration (Fig. REF B).
Analysis of the resulting pairwise flagellar interactions indicates a strong preference for AP synchronization,
though the IP is again observed (see SI Videos 2 & 3).
Accordingly, the phase stroboscope is now strongly peaked near \(\chi =\pi \)  (with \(S = 0.67\) ).
